1. Field of the Invention
This invention relates to a system for protecting wear parts in a vertical shaft centrifugal impact crusher.
2. Description of the Related Art
Material is crushed in a vertical shaft centrifugal impact crusher by being thrown off of a rotating table against anvils which are located around the periphery of the table. The table has impellers on it at spaced-apart locations about its periphery which cause the material to leave the table in the direction which will maximize fracture of the material as it strikes the anvils. The material being crushed is often quite abrasive and it causes considerable wear of the table parts, particularly the impellers. In addition, because the table parts become caked with dust from the material being crushed it often is quite difficult to remove them for replacement when they become worn. Some vertical shaft impact crushers employ an open table design where the impellers are releasably attached to mounting brackets which are permanently attached to the top of a single horizontal table. Other vertical shaft impact crushers employ a closed table design where impellers are sandwiched between upper and lower table elements. Closed table crushers have impellers which are less subject to wear than open table crushers, but it is much more difficult to replace them. Thus, the increased labor costs and costs of down time when replacement is necessary offsets the longer wear of the impellers.
Attempts have been made to protect the wear parts in vertical shaft impact crushers in the past. Britzke, et al., U.S. Pat. No. 5,954,282 disclose a crusher impeller that has horizontal bores at selected locations on its face. Tungsten carbide rods are then placed in these bores. However, this provides very localized protection and the impeller body will still wear between and around the rods. In addition, the rods can become displaced in the harsh environment in which these devices operate.
Britzke, et al. also disclose wear plates which cover the table between adjacent impellers. These wear plates not only protect the top surface of the table, but they have ramps that are located immediately in front of the associated impeller to cause the material to be thrown up onto the center part of the impeller face. While this does somewhat solve the problem of wear being concentrated near the bottom of impeller it creates a dead space above the ramp and even wear is still not obtained.
In one aspect of the subject invention, increased life is provided for the wear parts of an open table vertical shaft impact crusher by embedding in each impeller one or more rods which are made from material which is harder and more wear-resistant than the material the impellers are made from. The rods are oriented vertically and are located near the leading edge of the impeller at locations where the most wear occurs. Typically this would be near each side of the impeller, but one might be placed at the center as well. In a preferred embodiment of the invention the rods are tungsten carbide.
In another aspect of the invention, a bottom wear plate covers the upper surface of the table between the leading edge of each impeller and the back of the mounting bracket of an adjacent impeller. The bottom wear plate has a raised portion which is immediately adjacent to the leading edge of the impeller. A sloped ramp extends between the raised portion and the rest of the bottom wear plate.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.